I'm just confused that this cartridge was developed simply to be used in a 1 in 3" twist barrel.

Why not use any short, fat, mid-bore cartridge with a super fast twist?
You'd get the same results.

It's not as though we need some magical help from another wonder cartridge in dropping game animals.

Also, I'd bet that the 8.5mm bullet was chosen to eliminate the bullet petals from breaking off which makes the spinning effect through the gel more impressive.

Pretty neat experiment, but as mentioned above, barrel life with that twist and mono bullets will be quite short...

And, is there a limit in twist rate as it pertains to bolt actions vs auto loaders when pressures are concerned?
Does a fast twist (especially something as radical as 1 in 3) raise pressures to unacceptable ranges?